What was found
CLIMBING THROUGH FL 300, WITH AUTOPILOT ON AND FGC B IN CONTROL, "AILERON RATIO LOW" CAS MESSAGE APPEARS. AUTOPILOT BEGAN AN AGRESSIVE LT AND RT INPUT. HYD SYS NORMAL, WITH AUTOPILOT OFF INPUTS NORMAL. REMOVED BELLY PNL 166AB TO LOOK AT AILERON SELECTOR, CHECKED MODE ON FGC NAV. HDG + APP. NO FAULTS NOTED 8/27 SUSPECT PROX SWITCH CAUSING A/P TO CHANGE GAINS. REMOVED AND REPLACED OIL RUN RATIO PLOX SWITCH IAW 750MM 27-10-01 EICAS AILERON RATIO LOW. OPS CHECK GOOD IAW 750MM 27-10-01 INSTALLED ACCESS PNL'S 8/28.